A: Scientists have identified an estimated 4,000 species of freshwater snails, but one that you might find inhabiting your backyard pond or water garden is the Japanese Trapdoor Pond Snail, also known by its scientific name Viviparis malleatus.

These algae-eating gastropods have extra-special shells with a hinged fingernail-like plate that allows them to seal the shell’s opening, providing protection from drought and predation—hence their “Trapdoor Snail” nickname.

Though these hearty snails overwinter well in harsher northern climates, they do require some attention when temperatures dip. Here’s what you need to know:

Cool with Cold-Temperatures: These snails really do well in colder temperatures—in fact, some experts say they’ll do fine in sub-freezing weather, even down to 0 degrees Fahrenheit. When it gets really frigid, they’ll dive to the bottom of the pond, where the water is warmer.

Adequate Pond Depth Required: In order for them to be happy and healthy through those chilly winter spells, the snails need the water in your pond’s depth to ideally be 20 to 30 inches. Down there, they’ll happily groom the bottom of your pond, gobbling all the decaying matter like leaves, excess fish food and fish waste.

No Habitat Required: Because these little guys carry their homes on their back, you don’t need to provide shelter or food for them. If they feel endangered, they’ll disappear into their shells; if they’re hungry, they’ll nibble on algae that’s on your plants, underwater pots, rocks and walls.

Aeration Appreciated: Like any aquatic critter, Trapdoor Snails appreciate oxygen-rich water, and that’s where a subsurface aeration system, like the Airmax® PondAir™ Aeration Kit, will help. An adjustable unit like this will infuse your pond with oxygen while remaining whisper quiet.

If you have other types of snails in your pond or water garden, these rules may not apply—so be sure to learn their care requirements as they may need more attention than these hearty Trapdoor Snails.

Pond Talk: Do you have other types of snails in your pond? If so, what kind of care do they require?